Realistic neutron stars in the constant-Q branch of f(Q) gravity
Abstract
We investigate the hydrostatic equilibrium and global structure of neutron stars within symmetric teleparallel gravity, where gravitational interactions are mediated by the non-metricity scalar Q. Working within the metric-affine formulation, we adopt the regular, constant-Q branch (Q = Q*) of f(Q) gravity, which preserves regularity at the stellar centre while maintaining explicit dependence on the non-linear functional form through f(Q*) and its derivatives. We propose three novel non-linear f(Q) extensions: (i) a Born-Infeld-inspired model, (ii) a Hu--Sawicki analogue, and (iii) a Tsujikawa-inspired model. Incorporating state-of-the-art realistic unified equations of state, namely GPPVA(DD2) and SLy4, we numerically solve the modified Tolman-Oppenheimer-Volkoff equations and evaluate stellar stability via the Harrison-Zel'dovich-Novikov criterion. The Born-Infeld and Hu-Sawicki analogues smoothly recover the general relativistic limit as their control parameters increase, predicting stellar radii for low-mass objects (M < 2.0 M⊙) that match observational constraints from X-ray binaries and GW170817; however, their maximum masses remain capped below 2.43 M⊙ (DD2) and 2.06 M⊙ (SLy4). Conversely, the Tsujikawa-inspired model significantly stiffens the effective gravitational coupling, accommodating massive compact objects up to ∼ 3.36 M⊙ and offering a viable physical origin for the 2.59−0.09+0.08 M⊙ secondary object in GW190814, albeit at the expense of overpredicting radii for typical low-mass neutron stars. These contrasting behaviours demonstrate a key phenomenological complementarity between maximum mass and radius bounds within the constant-Q framework, highlighting the utility of multimessenger observations in constraining non-linear non-metricity gravity.
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BibTeX
@misc{bhattacharjee2026realistic,
title = {{Realistic neutron stars in the constant-Q branch of f(Q) gravity}},
author = {Debadri Bhattacharjee and Pradip Kumar Chattopadhyay and P. H. R. S. Moraes},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.36814},
eprint = {2610.36814},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.36814},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Realistic neutron stars in the constant-Q branch of f(Q) gravity
AU - Debadri Bhattacharjee
AU - Pradip Kumar Chattopadhyay
AU - P. H. R. S. Moraes
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.36814
UR - https://arxiv.org/abs/2610.36814
AB - We investigate the hydrostatic equilibrium and global structure of neutron stars within symmetric teleparallel gravity, where gravitational interactions are mediated by the non-metricity scalar Q. Working within the metric-affine formulation, we adopt the regular, constant-Q branch (Q = Q_*) of f(Q) gravity, which preserves regularity at the stellar centre while maintaining explicit dependence on the non-linear functional form through f(Q_*) and its derivatives. We propose three novel non-linear f(Q) extensions: (i) a Born-Infeld-inspired model, (ii) a Hu--Sawicki analogue, and (iii) a Tsujikawa-inspired model. Incorporating state-of-the-art realistic unified equations of state, namely GPPVA(DD2) and SLy4, we numerically solve the modified Tolman-Oppenheimer-Volkoff equations and evaluate stellar stability via the Harrison-Zel'dovich-Novikov criterion. The Born-Infeld and Hu-Sawicki analogues smoothly recover the general relativistic limit as their control parameters increase, predicting stellar radii for low-mass objects (M < 2.0 M_⊙) that match observational constraints from X-ray binaries and GW170817; however, their maximum masses remain capped below 2.43 M_⊙ (DD2) and 2.06 M_⊙ (SLy4). Conversely, the Tsujikawa-inspired model significantly stiffens the effective gravitational coupling, accommodating massive compact objects up to ∼ 3.36 M_⊙ and offering a viable physical origin for the 2.59_−0.09^+0.08 M_⊙ secondary object in GW190814, albeit at the expense of overpredicting radii for typical low-mass neutron stars. These contrasting behaviours demonstrate a key phenomenological complementarity between maximum mass and radius bounds within the constant-Q framework, highlighting the utility of multimessenger observations in constraining non-linear non-metricity gravity.
ER -